Dot Product and Angle Between Two Vectors

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Haven_Quartet

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Find the dot product and the angle between vectors v and w.

v = 2i + j

w = i + 2j

I know the dot product is 4.

I found the angle between both vectors to be 36°.

The angle between both vectors is 36.87°.

How do I find 36.87°?
 
Please show your work, so we can see what went wrong. Maybe you just rounded where you shouldn't.

In particular, what did you take the inverse cosine of?
 
Caffeine soaked greetings follow.
Haven_Quartet said:
Find the dot product and the angle between vectors v and w.

v = 2i + j

w = i + 2j

I know the dot product is 4.

I found the angle between both vectors to be 36°.

The angle between both vectors is 36.87°.

How do I find 36.87°?
Click to expand...
Hey there Haven_Quartet!
Welcome back buddy.
 
Caffeine soaked recall follows.
Haven_Quartet said:
Find the dot product and the angle between vectors v and w.

v = 2i + j

w = i + 2j

I know the dot product is 4.

I found the angle between both vectors to be 36°.

The angle between both vectors is 36.87°.

How do I find 36.87°?
Click to expand...
Repost from
mathhelpforum.com

Vectors v and w

mathhelpforum.com mathhelpforum.com
and at
mathforums.com

Vectors v and w

mathforums.com mathforums.com

I guess Plato's solution just wasn't explicit enough for you in the 1st thread and as usual, you still want further discussion of a solution that's already clear.
 
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Haven_Quartet said:
Yes but how do I find 36.87° without a calculator?
Click to expand...
You can use a trigonometric table.

This is a question like:

How do I dig a trench with bare hands?

Well it is very hard and probably not worth it. Go get a shovel - I mean calculator.

This particular problem, can be solved fairly easily (not with the accuracy of two-decimal places) with ruler-compass-protractor.
 
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